Pc Help Please

Hey, I upgraded my graphics card and PSU today and ever since Windows has been a lot slower - slower starting up and slower in general also. Performance is better in games though, which is good as that's why I bought the graphics card.
The light on my case is ALWAYS blinking and I can ALWAYS hear the little whirring sounds, both things that used to occasionally occur when opening a programme or generally when the computer was thinking, but when I check my CPU usage it is not high at all (at 5% right now). My memory is also only just under half full.
I cannot think what the problem is, I'm sure I've done something wrong - here are my specs: